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| Path | csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail |
|---|---|
| From | Jens Kallup <kallup.jens@web.de> |
| Newsgroups | de.comp.lang.assembler |
| Subject | Image deflaten |
| Date | Wed, 17 Jun 2020 14:59:49 +0200 |
| Organization | non-profit |
| Lines | 237 |
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Hallo Gemeinde,
ich habe hier einen Quellcode, den ich aus den Internet habe.
Ich habe diesen nach "nasm" konvertiert, so dass dieser auch
mit nasm übersetzt werden kann.
Die Sache ist nur die:
Wie wende ich diesen Code an?
Sprich, was muss ich machen, damit ein Image via 286/386 Code
seinen Dienst leistet.
Folgendes dazu:
- habe ein raw Image, das im MBR Sektoren ließt, und dann
verschiedene Sachen macht - eigentlich nur spielereien.
Am Bootsektor hängt noch dieser Code.
Danach folgt ein mit "lz4" (lzma4) (unter Linux erstelltes/komprimiertes
Image.
Habe kein MemoryPaging, und versuche, falls möglich, den Speicher
< 1MB zu nutzen.
Sprich es müsste ein "statischer" Speicher, der Groß genug ist für das
entpackte Image angelegt werden.
Doch wie macht man das, wenn keine "malloc" Funktion zur Verfügung
steht - nur ein reines BootImage?
Mit freundlichen Grüßen
Jens
; Decompresses Y. Collet's LZ4 compressed stream data in 16-bit real mode.
; Optimized for 8088/8086 CPUs.
;
; Code by Trixter/Hornet (trixter@oldskool.org) on 2013-01-05
; Updated 2019-06-17 -- thanks to Peter Ferrie, Terje Mathsen,
; and Axel Kern for suggestions and improvements!
;
; Updated 2019-06-30: Fixed an alignment bug in lz4_decompress_small
; Updated 2020-03-14: Speed updates: Pavel Zagrebin
[bits 16]
;---------------------------------------------------------------
; function lz4_decompress(inb,outb:pointer):word;
;
; Decompresses an LZ4 stream file with a compressed chunk 64K or less in
size.
; Input:
; DS:SI Location of source data. DWORD magic header and DWORD chunk size
; must be intact; it is best to load the entire LZ4 file into this
; location before calling this code.
;
; Output:
; ES:DI Decompressed data. If using an entire 64K segment, decompression
; is "safe" because overruns will wrap around the segment.
; AX Size of decompressed data.
;
; Trashes AX, BX, CX, DX, SI, DI
; ...so preserve what you need before calling this code.
;---------------------------------------------------------------
;Pavel Zagrebin is credited with the following speedups:
; Changing the end-of-file comparison to self-modifying offset
; push ds;pop ds->mov ds,bp
; adc cx,cx;rep movsb->jnc
; NOTE: I can't explain it, but with no extraneous background interrupts,
; timings are taking longer than normal on my IBM 5160. So, we have to
; reset our timing numbers here:
; Old timings: shuttle 85038 text 45720 robotron 307796 ---
; After Pavel's speedups:
; New timings: shuttle 81982 text 43664 robotron 296081 +++
;
---------------------------------------------------------------------------
section .text
global lz4_decompress
lz4_decompress:
push ds ;preserve compiler assumptions
les di,[lzmaBuffer_dst] ;load target buffer
push di ;save original starting offset (in case
!= 0)
lds si,[lzmaBuffer_src] ;load source buffer
add si,4 ;skip magic number
cld ;make strings copy forward
; mov bx, SHR4table ;prepare BX for XLAT later on
; lodsw ;load chunk size low 16-bit word
; mov bp,ax ;BP = size of compressed chunk
; lodsw ;load chunk size high 16-bit word
add bp,si ;BP = threshold to stop decompression
or ax,ax ;is high word non-zero?
jnz done ;If so, chunk too big or malformed, abort
starttoken:
lodsb ;grab token to AL
mov dx,ax ;preserve packed token in DX
; cs xlat ;unpack upper 4 bits, faster than SHR reg,cl
mov cl, 4
shr al, cl
mov cx,ax ;CX = unpacked literal length token
jcxz copymatches ;if CX = 0, no literals; try matches
cmp al,0Fh ;is it 15?
jne doliteralcopy1 ;if so, build full length, else start
copying
build1stcount: ;this first count build is not the same
lodsb ;fall-through jump as the one in the
main loop
add cx,ax ;because it is more likely that the
very first
cmp al,0FFh ;length is 15 or more
je build1stcount
doliteralcopy1:
rep movsb ;src and dst might overlap so do this
by bytes
;At this point, we might be done; all LZ4 data ends with five literals
and the
;offset token is ignored. If we're at the end of our compressed chunk,
stop.
cmp si,bp ;are we at the end of our compressed chunk?
mov word [cs:end_of_chunk+2],bp
;self-modifying cmp si,xxxx
mov bp,ds ;now we can use bp for restoring ds
jae done ;if so, jump to exit; otherwise, process
match
copymatches:
lodsw ;AX = match offset
xchg dx,ax ;AX = packed token, DX = match offset
and al,0Fh ;unpack match length token
cmp al,0Fh ;is it 15?
xchg cx,ax ;(doesn't affect flags); don't need ax
any more
je buildmcount ;if not, start copying, otherwise build
count
domatchcopy:
cmp dx,2 ;if match offset=1 or 2, we're
repeating a value
jbe domatchfill ;if so, perform RLE expansion optimally
xchg si,ax ;ds:si saved
mov si,di
sub si,dx
mov dx,es
mov ds,dx ;ds:si points at match; es:di points at
dest
movsw ;minimum match is 4 bytes; move them
ourselves
shr cx,1
jnc even
movsb
even:
movsw
rep movsw ;cx contains count-4 so copy the rest
xchg si,ax
mov ds,bp
parsetoken: ;CX always 0 here because of REP
xchg cx,ax ;zero ah here to benefit other reg loads
lodsb ;grab token to AL
mov dx,ax ;preserve packed token in DX
copyliterals: ;next 5 lines are 8088-optimal, do not
rearrange
; cs xlat ;unpack upper 4 bits, faster than SHR reg,cl
mov cl, 4
shr al, cl
mov cx,ax ;CX = unpacked literal length token
jcxz copymatches ;if CX = 0, no literals; try matches
cmp al,0Fh ;is it 15?
je buildlcount ;if so, build full length, else start
copying
doliteralcopy: ;src and dst might overlap so do this by bytes
rep movsb ;if cx=0 nothing happens
;At this point, we might be done; all LZ4 data ends with five literals
and the
;offset token is ignored. If we're at the end of our compressed chunk,
stop.
testformore:
end_of_chunk:
cmp si,256 ;this constant is patched with the end address
jb copymatches ;if not, keep going
jmp done ;if so, end
domatchfill:
je domatchfill2 ;if DX=2, RLE by word, else by byte
domatchfill1:
mov al,[es:di-1] ;load byte we are filling with
mov ah,al ;copy to ah so we can do 16-bit fills
stosw ;minimum match is 4 bytes, so we fill four
stosw
inc cx ;round up for the shift
shr cx,1 ;CX = remaining (count+1)/2
rep stosw ;includes odd byte - ok because LZ4
never ends with matches
adc di,-1 ;Adjust dest unless original count was even
jmp parsetoken ;continue decompressing
domatchfill2:
mov ax,[es:di-2] ;load word we are filling with
stosw ;minimum match is 4 bytes, so we fill four
stosw
inc cx ;round up for the shift
shr cx,1 ;CX = remaining (count+1)/2
rep stosw ;includes odd byte - ok because LZ4
never ends with matches
adc di,-1 ;Adjust dest unless original count was even
jmp parsetoken ;continue decompressing
buildlcount: ;build full literal length count
lodsb ;get next literal count byte
add cx,ax ;increase count
cmp al,0FFh ;more count bytes to read?
je buildlcount
jmp doliteralcopy
buildmcount: ;build full match length count - AX is 0
lodsb ;get next literal count byte
add cx,ax ;increase count
cmp al,0FFh ;more count bytes to read?
je buildmcount
jmp domatchcopy
done:
pop ax ;retrieve previous starting offset
sub di,ax ;subtract prev offset from where we are now
xchg ax,di ;AX = decompressed size
pop ds ;restore compiler assumptions
ret
section .data
lzmaBuffer_src: dw 0 ; decode: source of buffer pointer
lzmaBuffer_dst: dw 0 ; decode: destination
section .text
end_of_lz4:
Back to de.comp.lang.assembler | Previous | Next — Next in thread | Find similar
Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-17 14:59 +0200
Re: Image deflaten Stefan Reuther <stefan.news@arcor.de> - 2020-06-17 18:18 +0200
Re: Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-17 18:46 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-18 15:17 +0200
Re: Image deflaten "Peter J. Holzer" <hjp-usenet3@hjp.at> - 2020-06-23 11:31 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-23 22:06 +0200
Re: Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-24 01:38 +0200
Re: Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-24 01:46 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-24 14:33 +0200
Re: Image deflaten Stefan Reuther <stefan.news@arcor.de> - 2020-06-24 17:38 +0200
Re: Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-24 18:46 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-24 22:23 +0200
Re: Image deflaten Stefan Reuther <stefan.news@arcor.de> - 2020-06-25 18:30 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-26 11:35 +0200
Re: Image deflaten Stefan Reuther <stefan.news@arcor.de> - 2020-06-26 18:30 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-08-06 09:28 +0200
Re: Image deflaten "Peter J. Holzer" <hjp-usenet3@hjp.at> - 2020-06-26 18:39 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-08-06 09:29 +0200
Re: Image deflaten Stefan Reuther <stefan.news@arcor.de> - 2020-06-18 17:59 +0200
Re: Image deflaten Jens Kallup <kallup.jens@web.de> - 2020-06-18 19:26 +0200
Re: Image deflaten Bernhard Schornak <schornak@web.de> - 2020-06-18 19:59 +0200
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